The present invention relates to snap switches which within the terms of the present invention are mechanically operated switches which are switched abruptly by an external driving force from one switch position to a second position when the driving force reaches a defined critical value. The speed of switching between the switch positions is largely independent of the speed with which the driving force changes.
A snap switch of the type described above is known in which the snap switch is a leaf spring in which two parallel longitudinal slots separate a pair of outer arms from a central portion which extends longitudinally parallel to the outer arms. The central portion has an indentation across its entire breadth which reduces its thickness and thus increases its length. The increase in length of the central portion, when the length of the outer arms which form a frame around the central portion remains unchanged, results in biasing of the central portion which causes the central portion to curve to one or other side of the plane of the two outer arms, while the two outer arms are under tensile stress and remain flat. This known snap switch, of which the present invention is an improvement, has significant advantages over other known snap switches in which a snap spring and/or components thereof biased thereby are mounted on knife edges. The advantages of the snap switch described reside above all in the fact that when the switch is switched over it is only necessary to overcome internal frictional resistance which is minimal and above all constant, while the frictional resistance occurring on knife edges is greater from the start and can increase considerably and unpredictably as a result of wear. Moreover, the snap spring of the known snap switch of the type described is adapted to provide a conductive connection between the carrier and the switch contact mounted on the snap spring, because a good transfer of current between the carrier and the snap spring can be ensured by no more than a clamp connection. The contact resistance on knife edge bearings, on the other hand, is considerable from the start and can increase considerably as a result of dirt or wear. A disadvantage of the known snap switch of the type described is that the biasing of the snap spring resulting from the indentation and the associated increase in length of the central portion cannot easily be held sufficiently constant in mass production so that in the known snap switches when constructional details are the same considerable variations in the switching characteristics must be expected. Thus, as a result, predetermined conditions for the change of switch positions cannot be adhered to any more accurately with known snap switches of the type described than with the other known snap switches with knife edge bearings.